This invention relates in general to keyboard interfaces and in particular to a keyboard interface with an improved system for sensing and controlling the communication of data between the keyboard interface and a system interface.
In many computer systems, the input of data to a central processing system is by punching keys on a keyboard. The keyboard is normally equipped with a keyboard interface containing control logic for controlling the input information from the keys. In conventional technology, the keyboard interface communicates with the system interface through a data line and a clock line. The communication between the two interfaces is controlled by both interfaces. The system interface will need to communicate to the keyboard interface its status, such as interrupt signals to indicate that it is not yet ready to receive data. The system interface communicates its status by means of status signals to the keyboard interface through the same clock and data lines. In conventional keyboard interface systems, the status signals from the system interface are sensed through a sense clock line connected to the clock line and a sense data line connected to the data line. The data and clock lines also include gates to prevent the status signals from the system interface from otherwise affecting the keyboard interface.
In the above described conventional keyboard interface control system, a sensed clock line and a sensed data line as well as two gates are required. It is desirable to simplify the construction of the keyboard interface and to achieve cost savings by reducing the electronic components for achieving the same function and purpose. It is therefore desirable to provide an improved and simpler keyboard interface with fewer components.